Impact of silvicultural system on Cryphonectria parasitica incidence and on genetic variability in a chestnut coppice in Central Italy

This study was carried out in order to analyze the effect of silvicultural treatment on the structure and productivity of the chestnut stands, on the disease evolution and on the genetic structure of the species. The study considered a coppice stand aged 35 years (1994), growing on Monte Amiata (Tuscany, Italy). In the winter of 1994–1995, a low thinning of moderate intensity was applied; all suppressed shoots were removed, the intermediate class was partially reduced while the dominant storey was lightly thinned. Before, and after thinning, a description of stand structure, evaluation of number and typology of cankers caused by Cryphonectria parasitica on each tree and characterization of genotypical profile of all stumps was carried out. The structural and pathological surveys were repeated in February 1997 in order to analyze the growth trend of the stand and to verify the incidence and the evolution of disease two years after thinning. The results show that the applied silvicultural system neither reduced the genetic variability nor influenced the genotypic distribution of the stand. The removal of virulent cankers and the reduction of the individual susceptibility by the selection of the most vigorous trees has a positive effect on pathogen evolution.